Model experiments were conducted to investigate the seakeeping characteristics of a heavily loaded (55,000 lb.) Landing Vehicle Assault (LVA) planing hull. The vehicle under consideration has a flat-bottomed, zero deadrise angle planing surface with an adjustable full span transom stern flap and optional chine flaps. Experiments on the free-running 1/12 scale model, both with and without chine flaps were conducted at various speeds in simulated oblique irregular sea and coastal swell conditions. The intent of the investigation was to determine the craft habitability and safety of personnel as well as craft controllability. This information is presented herein in terms of wave induced craft vertical accelerations in standard one-third octave frequency bands. Additional plots are given for pitch, heave and roll accelerations. Vehicle responses to a 10 second period (full scale) swell are given in tabular form as acceleration transfer functions. Vertical acceleration levels at the bow and LCG were compared with MIL standards for maintaining personnel proficiency for one-hour. The results generally indicate the LVA accelerations to be within or at least marginally within acceptable levels. Some exceptions, particularly at the craft's bow, were noted in head and bow waves.